Sure and lots of times I can walk places. That doesn't mean bikes, cars, trains and planes aren't incredibly useful. They let me achieve things I can't in other ways for example transporting cargo without a team of people to help me. Just like AI coding.
Maybe your analogy holds if driving and walking took the same amount of time.
Plus "planning, implementing, validating, and reviewing" would be a bit like walking anyway in your analogy.
Would you still use your car if you ended up in the wrong destination half the time?
Yet replacing walking with cars is often cited as one of the reasons for many of society's ills.